In general plumbing work there is often a requirement to interconnect tubes end to end, whether those tubes be of the same material or not. Consequently it is necessary for plumbing suppliers to retain a large inventory of fittings, for example one fitting suitable for connecting to an end of a polyethylene tube, one fitting suitable for connecting to a copper tube, one fitting suitable for connecting to a lead pipe, and a combination of all those fittings. This is most inconvenient and expensive, and the main object of this invention is to provide a satisfactory fitting which can be used with a minimum of change over cost. For example, it is an object of the invention to provide a fitting comprising standard external parts, and sleeve and insert combinations which can be used for various types of tube or pipe, it being merely necessary to select the required inner elements to fit the fitting and be adaptable for securing the relevant pipe. The mathematical permutation for the abovementioned possibilities is six, whereas if another tube type (say British Standard Pipe) is added, the permutations total twenty-four, and therefore the above object can be regarded as seeking to (a) reduce inventory required for supplying the possible combinations, and (b) limit the variables to the inexpensive sleeves and inserts.
This problem has already been recognised, and the reader may refer to our Australian Patent No. 534,452 (the closest prior art known). The fitting disclosed therein is suitable for joining polyethylene or lead pipes, but was not suitable for joining copper or steel tubes. The invention disclosed herein is an extension of that earlier invention, and is directed primarily to the inclusion of copper or steel tubes to the pipes which may be included in those which can be joined with a single fitting, it being necessary merely to have alternative inserts and sleeves, and in some instances compression rings (olives).